The Midwest Hearth thermal switch (also known as a temp sensor or ‘snap-stat’)can automatically control the on/off function of your fireplace blower fan.TEMPERATURE RANGE: The switch will ‘close’ at 115 which allows power to thefan and turns it ‘on’. When the appliance temperature drops to 90 the switchwill ‘open’ and stop power to the fan shutting it ‘off’. WHEN USING ANOPTIONAL SPEED CONTROL: Simply set your preferred fan speed on the rheostatand leave it there. When the fireplace reaches 115 the blower willautomatically turn on and run at the speed you set on your speed control. LINEVOLTAGE: This switch is rated to run on standard household (plug in) voltage.IE: 115-120 VAC. This is the voltage almost all fireplace blower fans use foroperation. 15 AMP MAX: That’s 1800 watts at 120v… More than adequate forsingle and dual fireplace blowers.